There are many 'rocks' upon which people choose to build the foundation for their lives.
Some are good, and some are not so good.
Many people live from a purely materialistic, fatalistic, and selfish perspective; therefore, they build their lives upon financial success, personal notoriety, social popularity, comfort, pleasure, and individual glory. In a vacuum--in a world where other people don't feel the ripple effect of our actions--this may seem harmless. For an atheist-materialist this is the imagined vacuum-world of their lives.
But we all know that this isn't true.
Our actions have a rippling effect on others.
Then there are many decent people who have either a marginal religious perspective, or none at all, yet see the need for compassion, justice, equity, and the need for basic decency toward other people. Their foundational life-stones are philanthropic, beneficent, and tend toward a more decent society. Yet, like all human endeavors, their efforts soon fade, or are replaced with better, or worse, developments.
For building on the pebbles of human effort, though worthy of respect, brings nothing but the crumbling of effort in the erosion of human history.
Yet, there is One Rock which never crumbles under the pressure of popular society. One Rock which never erodes due to the relentless tide of change in temporal reality. One Rock which can never be buried under the dirt of deceit--since it is the Rock of the Resurrection of our Lord.
Little rocks of relativism, popular fads, scientism, socialism, communism, consumerism, hedonism, materialism, and agnosticism, may prop up the straw-hut of the fading man of this generation. But when the storm of change hits hard, it succumbs to the transformation of a new generation of temporal impostors. Yet, century after century, the Rock of Jesus Christ, in the Successor of St. Peter, in the Catholic Church, lays down its life as the foundational Stone for all who seek the immovable foundation of unchanging Truth and Love.
Life is as simple, and as difficult, as choosing which Rock to build our life upon. Why not choose the One which is the cornerstone of God's Mercy?